Doctors for paper-making and like machines



Nov. 27, 1962 H. E. B. SCOTT 3,055,486

DOCTORS FOR PAPER-MAKING AND LIKE MACHINES Filed Aug. 31, 1961 5Sheets-Sheet 1 INVENTOR FIG.4. m SCOTT BY 71m 770% VM ATTORNEYS Nov. 27,1962 H. E. B. scoTT 3,06

DOCTORS FOR PAPER-MAKING AND LIKE MACHINES Filed Aug. 51, 1961 5Sheets-Sheet 2 INVENTOR #512 5 co r- Woven 77% {7 0% ATTOINEY5 Nov. 27,1962 H. E. B. scor'r 3,065,486

DOCTORS FOR PAPER-MAKING AND LIKE MACHINES Filed Aug. 31, 1961 5Sheets-Sheet 3 FIGS.

INVENTOR fit 5 9C077 Wow 7% f'7/Z ATTORNEYS Nov. 27, 1962 H. E. B. scoTTDOCTORS FOR PAPER-MAKING AND LIKE MACHINES 5 Sheets-Sheet 4 Filed Aug.31, 1961 INVENTO'R #159 $0077 BY %0d641701% v ATTORNEYS Nov. 27, 1962 H.E. B. SCOTT 3,065,486

DOCTORS FOR PAPER-MAKING AND LIKE MACHINES Filed Aug. 31, 1961 5Sheets-Sheet 5 INVENTOR f/[B mrr 72/08; way/14 ATTORNE Y5 3,065,486Patented Nov. 27, 1962 fine 3,065,486 DOCTORS F611 PAPER-MAKING AND LIKEMACHENES Harold Eric Baliol Scott, Weybridge, Surrey, England, assignorto Vickerys Limited, London, England Fiied Aug. 31, 1961, Ser. No.135,325 Claims priority, application Great Britain Sept. 13, 1960 11laims. ((11. 15-25651) The invention has reference to doctors forpaper-making and like machines which incorporate rolls or cylinderswhich require to be maintained in a clean condition. The invention ismore specifically concerned with those of said machines in whichprovision must b made for the replacement of a worn doctor blade withoutstopping the machine. For example, in a machine for making crepe paperit is necessary to renew the doctor blade at very frequent intervals,due to the fact that the pressure of the blade against the fast-runningsurface of the cylinder causes the edge of the blade to be worn thin ata very considerable rate, and since the degree of crepe imparted to thepaper depends largely upon the width of the edge portion of the crepingdoctor blade by which the paper is taken from the creping cylinder.

In customary practice, when a creping doctor is to be changed, the paperweb is first interrupted with a cut-off doctor, the creping doctor isthen removed from contact with the cylinder, the worn blade is drawn outand a fresh blade inserted in its place after which the creping doctoris restored to its creping position, and the cut-off doctor is movedaway to permit of resumption of the feed of the paper web round thecylinder to the creping station. These operations are not onlytime-wasting but potentially dangerous to the machine operator since thedoctor blade must be changed while the blade holder is close to therotating cylinder; furthermore, since they must be carried out whilstthe machine remains running at high speed, a large quantity of paper isnecessarily run to waste during the blade-changing operation.

With a view to overcoming these difiiculties, the invention provides inor for a paper-making or like machine, a dual doctor assembly comprisingtwo oppositely directed doctor blades mounted on a support which isrotatable in a carrier to present the doctor blades alternatively to acylinder of the machine, and an automatic control system which can beset in motion under control of the machine operator, when a doctor bladerequires renewal, to cause movement of the carrier away from thecylinder and afterwards back again to its original position and to causerotation of the support in relation to the carrier, after the latter hascommenced to move away from the cylinder, to present the other doctorblade to the cylinder.

The worn doctor blade is thus moved into a position remote from thecylinder in which it can be removed at the operators leisure and withoutrisk of injury, and the other doctor blade is brought rapidly intooperative relation to the cylinder so that the wastage of paper isreduced to a minimum.

Preferably the automatic control system is effective to move a cut-offdoctor into operative position before the carrier moves away from thecylinder and to retract the cut-off doctor after the other doctor bladehas been presented to the cylinder.

Two embodiments of dual doctor assembly in accordance with the inventionwill now be described in more detail, by way of example, with referenceto the accompanying drawings in which:

, FIG. 1 shows in simplified form a creping cylinder of a paper-makingmachine and the associated doctors,

FIG. 2 is an end elevation of a first form of dual doctor assemblyaccording to the invention, showing one of the doctor blades inoperation,

FIG. 3 is a similar view showing the assembly in the position itoccupies during presentation of the other doctor blade to the crepingcylinder,

FIG. 4 is a diagram showing the automatic control system utilised withthe assembly shown in FIGS. 2 and 3,

'FIG. 5 is a side elevation of an alternative form of dual doctorassembly and FIG. 6 is a corresponding side elevation.

Like reference numerals indicate like parts throughout the figures.

FIG. 1 shows a creping cylinder 10 with an associated creping doctor 11,which strips the web 12 of paper from the cylinder and, in so doing,imparts crepe to it. In advance of the creping doctor 11 is a cut-01fdoctor 13 coupled at each side of the machine by an arm 34 to the pistonrod 35 of a piston mounted in an air cylinder 36. Air pressure in theair cylinders 36 normally holds the cut-01f doctor away from thecylinder 10 as shown. Beyond the creping doctor 11 is a cleaning doctor14.

The creping doctor 11 has dual doctor blades 16 as later described, andwhen it is desired to change the creping doctor blade the operatorpresses a button to initiate operation of the automatic control system.This causes the cut-oh doctor 13 to be presented to the cylinder 10 tointerrupt the feed of the web 12 to the creping station, the crepingdoctor assembly is then actuated to withdraw the worn creping doctorblade from the cylinder and present the other doctor blade to thecylinder in its place and finally the cut-off doctor is withdrawn to itsoriginal position clear of the cylinder to permit creping to be resumed.

The dual doctor assembly 11 shown in FIGS. 2 and 3 comprises asupporting beam 15 carrying a pair of diametrically opposite doctorblades 16, one of which is shown in FIG. 2 presented to the cylinder 10.The beam 15 is supported at opposite ends of the cylinder 10 by acarrier constituted by a pair of arms 17, one only of which is shown inFIGS. 2 and 3, pivoted at their lower ends 18 to the machine frame 19.Each arm 17 is connected by a link 20 to the piston rod 21 of a pistonmounted in an air cylinder 22. When air under pressure is admittted tothe left hand ends of the air cylinders 22 each of the arms is held, asshown in FIG. 2, against an adjustable stop 23. Adjustment of the stops23 serves to determine the angle at which the doctor blade 16 ispresented to the cylinder 10 and such adjustment can be made while themachine is running.

Pressure is applied to the doctor blade 16 by motors 24, one at eachside of the cylinder 10, each of which is connected through reductiongearing 25 to a pinion 26 meshing with a gear wheel 27 on the end of thebeam 15. The motors 24 tend to rotate the beam in a clockwise directionand air is admitted to them while the creping doctor is in operation.Under these conditions the motors 24- are stalled but apply operatingpressure to the doctor blade 16.

When the operator desires to change a worn blade he presses a button toset in operation an automatic control system which automaticallyperforms the following operations in sequence:

1) The cut-ofi doctor 13 (FIG. 1) is applied to the cylinder 10.

(2) Air pressure is cut oli from the motors 24, so releasing thepressure on the doctor blade 16.

(3) Air pressure is released from the air cylinders 22, so allowing thearms 17 to fall away from the cylinder 10 to the position shown in FIG.3 in which they are arrested by stops 28.

(4) While the arms 17 are so moving, air pressure is re-applied to theair motors 24 causing the beam 15 to rotate in a clockwise direction.

(5) When the worn doctor blade 16 has cleared the cylinder 10, airpressure is re-applied to the air cylinders 22, so causing the arms 17to move back towards the position shown in FlG. 2. During this movementthe beam 15 continues to rotate until the other doctor blade 16 comesinto contact with the cylinder 16, whereupon the air motors 24 stall andmaintain pressure on the doctor blade.

(6) The cut-off doctor 13 is lifted from the cylinder allowingresumption of creping of the paper web.

The operation of the automatic control system will now be explained withreference to FIG. 4. This shows the air cylinders 22 and 26 and the airmotor 24 at one side of the machine. Similar air cylinders and a similarair motor are, of course, provided at the other side of the machine andoperated in unison with those shown in' FIG. 4 under control of thevalves and the limit switches shown in the figure.

The control system includes two solenoid actuated control valves V Vwith which are associated pairs of solenoids S S and S 8.; respectively.When the dual doctor assembly is in its operative position the valve Voccupies a position such that air under pressure is admitted from an airsupply line 38 to the left hand end of the cylinder 36, the right handend of the cylinder 36 being connected to exhaust as indicated at 39.The valve V occupies a position such that air under pressure is suppliedfrom the line 38 to the air motor 24 and also, through a needle valve40, to the left hand end of the cylinder 22 which holds the doctorassembly against the creping cylinder.

To bring the other blade of the dual doctor assembly into operation, theoperator depresses the start button 37, so initiating the followingsequence of operations:

Depression of the button 37 momentarily energizes the Solenoid S socausing the valve V to move to its alternative position, thus reversingthe pressure and exhaust connections to the cylinder 36 which lowers thecut-off doctor 13 (FIG. 1) on to the machine cylinder 10. When thepiston in the cylinder 36 has nearly completed its stroke a cam 41 onits piston rod 35 actuates a limit switch LS1 to energise the solenoidThis causes the valve V to move to its alternative position, cutting offthe air supply to the air motor 24 and allowing air to leak from thecylinder 22 to an exhaust connection 42 through the needle valve 40. Thearms 17 (FIG. 22.)

supporting the doctor assembly accordingly fall away from the machinecylinder 10.

As the piston in the cylinder 22 nears the end of 1ts stroke, a cam 43on its piston rod 21 actuates a limit switch LS2, so energising thesolenoid S and causing the valve V to return to its original position.Air under pressure is accordingly re-admitted to the air motor 24 whichcommences to rotate the beam (FIG. 2). Air under pressure is alsore-admitted to the cylinder 22 so causing the dual doctor assembly toreturn towards the machine cylinder. Just before the piston rod 21 isfully retracted into the cylinder 22 the cam 43 operates a limit switchLS3, so energising the solenoid S and causing the valve V to return toits original position. As the result the air connections to the cylinder36 are reversed and the cut-off doctor is lifted from the machinecylinder. The parts are now back in their original position.

It should be noted that the cam 41 operates the limit switch LS1 onlywhen it moves to the left and not when it returns to the right.Similarly the limit switch LS3 is operated by right hand movement onlyof the cam 43. A non-return valve 44 is provided in the air supply km 38so that if the air pressure should fail the dual doctor assembly cannotfall away from the machine cylinder.

The dual doctor assembly 11 shown in FIGS. 5 and 6 operates on the samegeneral principle. Again two opposed doctor blades 16 are provided on abeam 15 which is rotatable in a carrier constituted by a pair of arms17, which in this case are pivoted at their upper ends 18 to the machineframe. Each arm 17, as before, is associated with an air cylinder 22 formoving it towards and away from the cylinder 10. Rotary movement isimparted to the beam 15 by an electric motor 48 at one side of themachine which is connected to the beam 15 through worm and worm wheelgearing 29. Operating pressure is applied to the blade 16 by the aircylinders 22 and its angle of presentation to the cylinder 10 iscontrolled by adjustable screws 30 carried by the piston rods 31 ofpistons 32 mounted in air cylinders 33 situated at opposite sides of themachine. The screws 30 can be adjusted to vary the inclination of theblade 16 while the machine is running.

The assembly has a similar automatic control system to that alreadydescribed. The sequence of operations following pressure on the controlbutton is as follows:

(1) The cut-off doctor 13 (FIG. 1) is presented in the cylinder 10.

(2) The pressure and exhaust connections to the cylinders 22 arereversed, causing the arms 17 to move away from the cylinder 16.

(3) The pressure and exhaust connections to the cylinders 33 arereversed, so lifting the screws 30 clear of the path of the doctor blade16.

(4) Current is supplied to the motor 48, causing the beam 15 to rotatein an anticlockwise direction.

(5) When the worm blade has passed clear of the screws 39 theconnections to the cylinders 33 are again reversed to return the screwsto the position shown in FIG. 5.

(6) When the other doctor contacts the screws 32 a limit switch isactuated to stop the motor 48.

(7) The connections to the cylinders 22 are reversed to restore the arms17 to the position shown in FIG. 5. (8) The cut-off doctor 13 is liftedfrom the cylinder 14).

What I claim as my invention and desire to secure by Letters Patent is:

1. A doctor assembly for doctoring the cylinder of a paper-making orlike machine comprising a carrier, a support carrying two oppositelydirected doctor blades and mounted for rotation in said carrier topresent the doctor blades alternatively to said cylinder, a cut-offdoctor movable from a normal inoperative position to an operativeposition in which it contacts said cylinder, and an automatic controlsystem adapted to be set in motion when a doctor blade requires renewaland operative first to move the cutoff doctor to its operative position,then to move the carrier away from the cylinder and back again, torotate the support in relation to the carrier, after said carrier hascommenced to move away from the cylinder to present the other doctorblade to the cylinder, and finally to return the cut-off doctor to itsinoperative position after said other doctor blade has been presented tothe cylinder.

2. A doctor assembly as claimed in claim 1, which includes a stopmechanism which is adjustable while the machine is running to vary theangle of presentation of the doctor blade to the cylinder.

3. A doctor assembly as claimed in claim 2, wherein said carrier ispivoted to the machine, said control system includes an air cylinder formoving the carrier towards and away from the cylinder of the machine andthe adjustable stop mechanism is effective to limit the movement of thecarrier towards the cylinder of the machine.

4. A doctor assembly, as claimed in claim 1, which includes an air motorfor rotating the support in relation to the carrier which runs stalledto maintain pressure on the doctor blade presented to the cylinder andin which the control system is effective to stop the air motor prior tomovement of the carrier away from the cylinder.

5. A doctor assembly, as claimed in claim 1, which includes anadjustable stop mechanism bearing against the doctor to control theangle of presentation of the doctor blade to said cylinde and whereinthe control system is effective to withdraw the stop mechanism from thedoctor prior to rotation of the support in relation to the carrail rier,and afterwards to return it into operative relation with the otherdoctor blade.

6. A doctor assembly as claimed in claim 5, wherein the control systemincludes air cylinders tor respectively moving the carrier away from andtowards the cylinder and for moving the stop mechanism into and out ofits operative position, and a motor for rotating the support in relationto the carrier.

7. A dual doctor assembly for doctoring a cylinder of a paper-making orlike machine, comprising a carrier mounted for movement in said machine,a support carrying two oppositely directed doctor blades and mounted forrotation in the carrier to present said doctor blades alternatively tothe cylinder means for applying yielding operating pressure to thedoctor blade presented to said cylinder, and a control system operable,when it is desired to renew a doctor blade, to movesaid carrier awayfrom the cylinder and then back again and to rotate the support inrelation to the carrier, after the carrier has begun to move away fromthe cylinder, to present the other blade to the cylinder.

8. A dual doctor assembly for doctoring a cylinder of a paper-making orlike machine, comprising a carrier mounted for movement in said machine,a support carrying two oppositely directed doctor blades and mounted forrotation in the carrier to present said doctor blades alternatively tothe cylinder, a normally stalled air motor coupled to drive said supportand applying yielding operating pressure to the doctor blade presentedto the cylinder, a control system operable, when it is desired to renewa doctor blade, to move said carrier away from the cylinder and thenback again and to permit said air motor to rotate the support inrelation to the carrier, after the carrier has begun to move away fromthe cylinder, to present the other blade to the cylinder.

2. A doctor assembly as claimed in claim 8, which ineludes an aircylinder coupled to the carrier and normally eifective to urge ittowards the cylinder about a pivot and an adjustable stop coacting withsaid carrier to limit its movement towards the cylinder, said controlsystem including a valve controlling the exhaust of air from and itsadmission to said air cylinder to effect movement of the carrier awayfrom and back to the cylinder.

10. A dual doctor assembly for doctoring a cylinder of a paper-making orlike machine, comprising a carrier pivoted to said machine, a supportcarrying two oppositely directed doctor blades and mounted for rotationin the carrier to present said doctor blades alternatively to thecylinder, an air cylinder which is normally effective to maintain saidcarrier in position to apply yielding operating pressure to the doctorblade presented to the machine cylinder, a normally inoperative motorfor imparting rotation to the support and a control system operable,when it is desired to renew a doctor blade, to condition said aircylinder to cause the carrier to move away from the cylinder and backagain and to render said motor efiective to rotate the support aftersaid carrier has commenced to move away from the cylinder.

11. A doctor assembly as claimed in claim 10, which includes anadjustable abutment coasting with the doctor to control the angle ofpresentation of the doctor blade to the cylinder and wherein the controlsystem includes mean for withdrawing said abutment from the doctor bladeprior to rotation of the support and afterwards returning it to positionto coact with the other blade.

References Cited in the file of this patent UNITED STATES PATENTS2,474,052 Johnson June 21, 1949 2,698,453 Garrow Jan. 4, 1955 FOREIGNPATENTS 141,982 Australia July 4, 1951

